This research will study synaptic mechanisms in the innerplexiform layer of carp and mudpuppy retinas, and the effects of pharmacological environmental manipulations of those synaptic mechanisms on the functional properties of the retinal network. The nature of putative neurotransmitters acting on IPL synapses, transmitter-receptor interactions, and receptor structural specificity, and the membrane ionic mechanisms underlying postsynaptic responsiveness to the transmitters, are some of the features of these studies. Synaptic transmission will be manipulated by the use of agonists, antagonists, and modulators, identified as effective in the studies, and environmental variables such as temperature and extracellular ionic concentrations. The transfer properties of the retina will be characterized by nonlinear system analytic techniques, such as sum-of-sinusoids (Victor) noise inputs and frequency kernel or Volterra coefficient output representation. Changes in the transfer properties will be related to the manipulations of specific synaptic mechanisms.